Fire alarm device



May 24, 1955 L. T. WARD 2,708,895

FIRE ALARM DEVICE Filed Aug. 16, l954 INVENTOR ZAW/PfA CE Z M/PD BYHM; g

ATTO R N EY United States Patent FIRE ALARM DEVICE Lawrence T. Ward, Northampton County, Pa. Application August 16, 1954, Serial No. 450,173 3 Claims. (Cl. 116-106) This invention relates to a device which emits an audible sound when activated by intense heat and more particularly it relates to an alarm device having a container of gas or vapor under pressure and means for releasing said gas when a critical temperature is attained.

It is an object of this invention to provide a portable fire alarm device.

It is another object of this invention to provide a fire alarm device set off by the melting of a fusible mass.

It is another object of this invention to employ a fusible mass which does not come in contact with gas or vapor being emitted from the container.

It is a further object of this invention to provide an inexpensive portable fire alarm device so that a plurality of such devices may be disposed about a building.

These and other objects and purposes of this invention will become evident upon reading the following descriptive disclosure taken in conjunction with the accompanying drawing in which:

Fig. l is a front view of the alarm device,

Fig. 2 is a view taken on line 2-2 of Fig. 1,

Fig. 3 is a view taken on line 3-3 of Fig. 2 and show ing the device with an activating spring in a cocked or energized position,

Fig. 4 is a view similar to that of Fig. 3 but showing the device with the activating spring in a de-energized position after fracturing a frangible finger element, and

Fig. 5 is a view taken on line 55 of Fig. 2 and showing the manner of maintaining the activating spring in a cocked or energized position.

The major defect of using an aerosol bomb having a fusible plug as a fire alarm device, is that the plug is disposed in an aperture in the container top wall.

The presence of intense heat causes the plug to melt but the rush of gas or vapor under pressure through a crevice of the melting plug causes the plug to cool, so that a plug adapted to melt at a definite or fixed temperature actually does not melt sufficiently at that temperature to operate the alarm due to the herein above disclosed cooling effect caused by expanding gases or vapors.

In applicants device the fusible material does not come in contact with the gas or vapors being emitted under pressure, so that the device always operates at a fixed temperature, for example, 140 R, which is the melting point of the fusible mass.

Turning now to the drawing and particularly to Fig. 1, a container preferably of a cylindrical configuration is preferably provided with a handle 11. The top of the container may be provided with tiered set-back closure element 12 having an orifice circumscribed by an inverted U-shaped rim 13 (Figs. 3 and 4).

A container cap 14 also having an inverted U-shaped rim 13x is disposed within the top container orifice so that rim 13x is disposed upon rim 13. Preferably some organic adhesive sealing compound is disposed between rims 13x and 13 to efiect a gastight seal therebetween.

The cap 14 is provided with a frangible finger element 15 preferably made of glass and having a tubular cavity 16 centrally disposed therein. The finger element 15 is provided with a circular base or rim 17 adapted to engage a protuberant cylindrical wall 18 disposed centrally in said cap 14. The wall 18 is provided with a ledge 19 adapted to engage the top surface of rim 17 between the engaging surface of which some sealing compound is preferably disposed. Other conventional means of effecting a gastight seal between finger 15 and wall 18 are operable.

The finger 151's preferably provided with a constricted section 20 where the thickness of the glass constituting the finger wall is relatively thin.

This constricted section 20, being weak compared to the remainder of finger element 15, is fractured when that portion of thefinger disposed thereabove is given a sharp blow.

The cap 14 is further provided with a second aperture into which a holder strip 21 is sealingly secured by press fitting, preferably with the aid of conventional sealing compound, to produce a gas tight seal. The holder strip is provided with a screw threaded well portion 22 and a pair of wing portions 23 each having a depending recess adapted to hold a spring foot therein (Fig. 5). The strip 21 may be spot welded to the cap 14, if desired.

A. swingable energizing spring 24 having a pair of spaced apart feet and of a strength suitable to fracture the finger element 15 is secured within the recesses of the wing portions 23 of holder strip 21. A screw threaded cylindrical pillar 25 is threaded into the well of the strip 21. A circular plate 26 is secured to the top of pillar 25 by means of fusible metal 27 (Figs. 2 and 3) circularly disposed in the angle formed between plate 26 and pillar 25.

The spring 24 is preferably made of wire having a pair of spaced apart feet 28 adapted to be secured within the recesses of wing portions 23. A single coil is disposed adjacent each foot 28 and an arcuate bridge section 29 (Fig. 2) joins the spaced apart coils.

A dome 30 is press fitted and preferably sealed, by means of conventional sealing and securing substance 31, to rim 15. The dome is of such a height as to conventionly enclose finger element 15 in an upright position. The dome 30 is provided with an outlet opening 32 to which a whistle, or horn, or other conventional gas operated alarm 33 is secured.

The device may be set upon the floor but preferably it is hung from suitable brackets near the ceiling by means of handle 11, since the heat of a fire is most intense near the ceiling.

In operating the device, the depressed or cocked spring bridge 29 engages the underside of plate 26 away from finger element 15 (Fig. 3). The intense heat of a fire causes the fusible material 27 to melt, thereby in turn causing spring bridge-.29 to dislodge plate 26 and to sharply strike the glass finger 15 above the constricted section 20 causing the finger to break at this point (Fig. 4).

The released gas or vapor from the container then rushes into the cavity of dome 30 and outwardly through opening 32 causing the alarm horn or whistle to operate, giving a warning that a fire has started.

This invention has been described by means of an illustrative embodiment but clearly other embodiments fall within its generic scope. Thus the pillar 25 need not be screw-threaded into a well of strip 21 since it could be secured by being welded directly to cap 14. Other noninventive modifications will also occur to those skilled in the art, but all these modifications are intended to be embraced within the scope of the claims herein. Thus also the alarm could be made to operate as a fire extinguisher,

if carbon tetrachloride is added with Freon as the volatile gas disposed in the container.

I claim:

1. A fire alarm device comprising, a pressure resistant container for confining fluid and provided with a flat top wall, a frangible tubular element secured to said top wall and having an opening connecting with the interior of the container to provide an outlet flow for the contained fluid, an energized spring secured to said top wall to one side of and adapted to fracture said frangible element upon de-energization thereof, means for securing said spring to said top Wall, a well having internal threads secured in said top wall between said energized spring and said frangible element, a threaded pillar threadingly disposed in said well, a plate disposed upon said pillar, T

means for fusibly securing said plate to said pillar adapted to melt at a fixed temperature means whereby said plate holds the spring in energized condition, a gas tight dome disposed over said container top wall hermetically sealed to said container and provided with an outlet opening, and whistle means secured in said dome outlet opening.

2. The apparatus of claim 1 wherein said spring consists of a pair of spaced-apart coil elements joined by an integral bridge piece, each of said coils having an integral longitudinal foot, and wherein said means for securing said spring is a holder strip having spaced-apart channels therein adapted to engage said longitudinal foot of each of said coil elements.

3. The apparatus of claim 2 comprising a handle swingably secured to the container and adapted to be hung from a ceiling for positioning said fire alarm near the ceiling where the heat of a fire accumulates, said frangible tubular element being provided with a weakened annular wall section of diminished thickness and adapted to fracture easily, and said coils of said spring being disposed on opposed sides of said tubular element to facilitate fracture of the tubular frangible element at its weakened annular wall section.

References Cited in the file of this patent UNITED STATES PATENTS 1,962,695 Pohl June 12, 1934 2,034,179 Franklin Mar. 17, 1936 2,590,770 Hirschle Mar. 25, 1952 

